Data storage systems commonly employ continuous data protection (CDP), also known as “continuous replication,” for protecting the data they store. Continuous replication operates on storage volumes, such as LUNs (Logical Unit Numbers), using Fibre Channel or iSCSI (Internet Small Computer System Interface), for example, to replicate data writes performed on storage volumes at a source to replicas of the storage volumes at a destination. Continuous replication generally allows administrators to restore data to any desired point in time.
Continuous replication may be performed synchronously or asynchronously. “Synchronous” replication proceeds in band with IO requests as the requests are processed at the source. The source typically sends data specified in the IO requests to the destination on an individual basis, e.g., one-by-one, as the source processes the IO requests. In contrast, “asynchronous” replication proceeds out of band with individual IO requests, with replicas updated, for example, on demand, at regular intervals, and/or in response to particular events.
A well-known solution for continuous replication is the RecoverPoint system available from EMC Corporation of Hopkinton, Mass. RecoverPoint systems include a replication splitter and one or more local replication appliances, at both a source data storage system and a destination data storage system. As the source processes IO requests that specify data to be written to a particular volume, the replication splitter at the source intercepts the IO requests and sends them to the local replication appliance. The replication appliance at the source communicates with the replication appliance at the destination, and the two appliances orchestrate the storage of the data specified in the IO requests at the destination. In this manner, the destination is made to store a current, or near-current, redundant copy of the volume, and the redundant copy may provide any-point-in-time recovery in the event of a failure at the source.